High-Responsivity and High-Speed Waveguide Photodiode With a Thin Absorption Region

The characteristics of a waveguide photodiode with a thin absorption layer are reported. A responsivity of 1.08 A/W at 1.55 mu m was measured using a 0.1-mu m-thick absorption region with a polarization dependence of less than 0.25 dB. A thin absorption layer enables us to use a thicker intrinsic layer. Using a thicker intrinsic region of 0.9 mu m and an adiabatically reduced waveguide width, a bandwidth of 42 GHz was achieved. Adopting a tapering waveguide width did not give rise to a degradation of responsivity or alignment tolerance.